Re: [RFC XEN PATCH v8 5/5] domctl: Add XEN_DOMCTL_gsi_permission to grant gsi

["Chen, Jiqian" <Jiqian.Chen@xxxxxxx>]

On 2024/6/5 18:09, Jan Beulich wrote:
> On 05.06.2024 09:04, Chen, Jiqian wrote:
>> On 2024/6/5 01:17, Jan Beulich wrote:
>>> On 04.06.2024 10:18, Chen, Jiqian wrote:
>>>> I tried to get more debug information from my environment. And I attach 
>>>> them here, maybe you can find some problems.
>>>> acpi_parse_madt_ioapic_entries
>>>>    acpi_table_parse_madt(ACPI_MADT_TYPE_INTERRUPT_OVERRIDE, 
>>>> acpi_parse_int_src_ovr, MAX_IRQ_SOURCES);
>>>>            acpi_parse_int_src_ovr
>>>>                    mp_override_legacy_irq
>>>>                            only process two entries, irq 0 gsi 2 and irq 9 
>>>> gsi 9
>>>> There are only two entries whose type is ACPI_MADT_TYPE_INTERRUPT_OVERRIDE 
>>>> in MADT table. Is it normal?
>>>
>>> Yes, that's what you'd typically see (or just one such entry).
>> Ok, let me conclude that acpi_parse_int_src_ovr get two entries from MADT 
>> table and add them into mp_irqs. They are [irq, gsi][0, 2] and [irq, gsi][9, 
>> 9].
>> Then in the following function mp_config_acpi_legacy_irqs initializes the 
>> 1:1 mapping of irq and gsi [0~15 except 2 and 9], and add them into mp_irqs.
>> But for high GSIs(>= 16), no mapping processing.
>> Right?
> 
> On that specific system of yours - yes. In the general case high GSIs
> may have entries, too.
> 
>> Is it that the Xen hypervisor lacks some handling of high GSIs?
> 
> I don't think so. Unless you can point out something?
Ok, so the implementation is still to get mapping from mp_irqs, I will change 
in next version.
Thank you.

> 
>> For now, if hypervisor gets a high GSIs, it can't be transformed to irq, 
>> because there is no mapping between them.
> 
> No, in the absence of a source override (note the word "override") the
> default identity mapping applies.
What is identity mapping? Like the mp_config_acpi_legacy_irqs does?

> 
> Jan

-- 
Best regards,
Jiqian Chen.